CVE-2026-53361 is an unprivileged, container-escapable use-after-free vulnerability in the AF_UNIX socket garbage collector. The bug occurs when a concurrent MSG_PEEK on an in-flight file descriptor takes a reference the GC's census never counts, allowing the collector to free a socket still in use and leave a dangling sk_buff. The gc_in_progress flag fails to block the peek mid-run, enabling the race condition.

This issue was previously addressed in CVE-2021-0920, CVE-2026-23394, and CVE-2026-53361 (patch d82ba05263c6). Affected kernels include 6.12.94, 6.17.0-41, and others, with patches available. The exploit targets specific kernel versions, excluding 7.x and Ubuntu 6.8 GA.

CPU count and SLUB cache armoring notes are also mentioned, with recommendations for additional hardening.